Ground tracking devices and methods for use with a utility locator

ABSTRACT

A ground tracking apparatus for connection to a locator or other measurement device and configured to determine position, motion, and/or orientation information is disclosed. The ground tracking apparatus may include a ground follower assembly including one or more wheels, which may be detachably coupled to a buried object locator system to capture three-dimensional positional and orientation information during a locate process, as well as provide output data or information to be integrated with maps, photographs, drawings, or other data or information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to co-pendingU.S. patent application Ser. No. 13/161,183, entitled GROUND-TRACKINGDEVICES FOR USE WITH A MAPPING LOCATOR, filed on Jun. 15, 2011. Thisapplication also claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application Ser. No. 61/377,215, entitled GROUNDTRACKING DEVICE FOR A MAPPING LOCATOR, filed on Aug. 26, 2010, and toU.S. Provisional Patent Application Ser. No. 61/355,035, entitledMECHANICAL GROUND TRACKING DEVICE FOR A MAPPING LOCATOR, filed on Jun.15, 2010. The content of each of these applications is herebyincorporated by reference herein in its entirety for all purposes.

This application is also related to U.S. Provisional Patent ApplicationSer. No. 60/730,124, entitled SELF-STANDING MAPPING SONDE AND LINELOCATOR EMPLOYING IMPROVED DISPLAY METHODS WITH INTEGRALGROUND-PENETRATING RADAR AND OTHER DETACHABLE DETECTION APPARATUS, filedon Oct. 24, 2005, and to U.S. Provisional Patent Application Ser. No.61/262,852, entitled IMAGE-BASED MAPPING LOCATOR SYSTEM, filed Nov. 19,2009. The content of each of these applications is hereby incorporatedby reference herein in its entirety for all purposes.

FIELD

The present disclosure relates generally to systems, methods, andapparatus for locating buried objects (“locators”). More specifically,but not exclusively, the system relates to ground tracking devices forattachment to locators or other measurement devices to follow a groundor other surface and provide position and/or motion information inmultiple axes of motion.

BACKGROUND

There are many situations where is it desirable to locate buriedutilities or other objects, such as pipes and cables. For example, priorto starting any new construction that involves excavation, it isimportant to locate buried objects, such as underground utilities likepower lines, gas lines, phone lines, fiber optic cable conduits, CATVcables, sprinkler control wiring, water pipes, sewer pipes, and the like(collectively and individually referred to herein as “utilities” or“objects”). As used herein the term “buried” refers not only to objectsbelow the surface of the ground, but also to objects located insidewalls, between floors in multi-story buildings, cast into concreteslabs, or otherwise obscured, covered, or hidden from direct view oraccess.

Location of these buried objects may be important for cost, time, andsafety reasons. For example, if a backhoe or other excavation equipmenthits a high voltage line or a gas line, serious injury and propertydamage may result. Severing water mains and sewer lines leads to messycleanups. The destruction of power and data cables can seriously disruptthe comfort and convenience of residents and create huge financiallosses.

Buried objects can be located by sensing an emitted electromagneticsignal. For example, some buried cables, such as electric power lines,are already energized and emit their own long cylindricalelectromagnetic field. In other cases, the buried object may beenergized to produce electromagnetic radiation. For example, an externalelectrical power source having, for example, a frequency in a range ofapproximately 50 Hz to 500 kHz may be used to energize a buried objectsuch as a pipe or conduit. Location of buried long conductors is oftenreferred to as “line tracing,” and the results may be referred to as a“locate.”

SUMMARY

The present disclosure relates generally to systems, methods, andapparatus for locating buried objects (“locators”). More specifically,but not exclusively, the disclosure relates to ground tracking devicesfor attachment to locators or other measurement devices to follow aground or other surface and provide position and/or motion informationin multiple axes of motion.

For example, in one aspect, the disclosure relates to a ground trackingdevice. The ground tracking device may include a ground followerassembly, and a mounting assembly configured to floatably attach theground follower assembly to a measurement device. The ground followerassembly may be configured to generate one or more output signalsrepresentative of a motion of the measurement device over a groundsurface in two or more axes or dimensions of motion.

In another aspect, the disclosure relates to a ground tracking device.The ground tracking device may include, for example, a wheel, a wheelsensor element configured to measure a rotation of the wheel andgenerate a wheel rotation output signal corresponding to the rotation ofthe wheel, a swing arm assembly coupled at a first end to the wheelassembly, a yoke assembly coupled at a second end of the swing armassembly, a swing arm sensor element configured to sense a rotary motionof the second end of the swing arm assembly and generate a swing armrotation output signal corresponding to the rotary motion of the swingarm assembly, and a yoke sensor element configured to sense a rotationof the yoke assembly relative to a centerline of a measurement deviceand generate a yoke rotation signal corresponding to the rotation of theyoke assembly.

In another aspect, the disclosure relates to a dual wheel groundtracking device. The ground tracking device may include, for example, awheel arm structure assembly, a first wheel coupled to the wheel armstructure assembly, a first wheel sensor element configured to measure arotation of the first wheel and generate a first wheel rotation outputsignal corresponding to the rotation of the first wheel, a second wheelcoupled to the wheel arm structure assembly and the first wheel, asecond wheel sensor element configured to measure a rotation of thesecond wheel and generate a second wheel rotation output signalcorresponding to the rotation of the second wheel, a yoke assembly, awrist joint assembly coupled between the wheel arm structure assemblyand the yoke assembly, a yoke sensor element configured to sense arotation of the yoke assembly relative to a centerline of a measurementdevice and generate a yoke rotation signal corresponding to the rotationof the yoke assembly, and a wrist joint sensor element configured tosense a movement of the wheel arm structure assembly relative to theyoke assembly and generate a wheel arm movement signal corresponding tothe movement of the wheel arm structure assembly relative to the yokeassembly.

In another aspect, the disclosure relates to a ground tracking locatorsystem. The ground tracking locator system may include a portablelocator, and a ground tracking device. The ground tracking device mayinclude a ground follower assembly, and a mounting assembly configuredto floatably attach the ground follower assembly to the portablelocator. The ground follower assembly may be configured to generate oneor more output signals representative of a motion of the locator deviceover a ground surface in two or more axes or dimensions of motion.

Various additional aspects, features, functions, and details are furtherdescribed below in conjunction with the appended Drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates use of an embodiment of a ground tracking systemincluding a ground tracking device and a locator in accordance withaspects of the present disclosure.

FIG. 1B illustrates details of example movements of a locator andattached ground tracking device about a substantially fixed groundreference point in accordance with aspects of the present disclosure.

FIG. 1C illustrates details of example movements of a locator andattached ground tracking device in up/down directions or elevationsabove a ground or other surface in accordance with aspects of thepresent disclosure.

FIG. 1D illustrates details of example side-to-side movements of alocator and attached ground tracking device in accordance with aspectsof the present disclosure

FIG. 1E illustrates details of an embodiment of a ground tracking deviceincluding a spherical ground following element in accordance withaspects of the present disclosure.

FIG. 2 is an enlarged rear isometric view of the exterior of the groundtracking system embodiment of FIG. 1A illustrating external components.

FIG. 3 and FIG. 4 are enlarged bottom elevation and side elevationviews, respectively, illustrating example degrees of freedom of motionof the embodiment of FIG. 1A.

FIG. 5 is an exploded isometric view of the embodiment of FIG. 2.

FIG. 6 is an isometric view of a main printed circuit board (PCB) of theembodiment of FIG. 5.

FIG. 7 is a fragmentary bottom plan section view taken along line 7-7 ofthe embodiment of FIG. 4, illustrating the location of a sensor andshielded magnet at two of the pivot points.

FIG. 8 is fragmentary vertical section view taken along line 8-8 of theembodiment of FIG. 3, illustrating details of the magnetic sensorarrangement where the yoke connects to the lower antenna enclosure of alocator.

FIG. 9 is an enlarged section view of a typical sensor assemblyincluding a magnetic sensor, magnetic shield, and permanent magnetarrangement that may be used in various embodiments to generatepositional information at pivot points.

FIG. 10 is a section view taken along line 10-10 of the embodiment ofFIG. 9.

FIG. 11 is a diagrammatic illustration of another embodiment of a groundtracking system including a ground tracking device and a locator inaccordance with aspects of the present disclosure.

FIG. 12 is an enlarged rear isometric view of the embodiment of FIG. 11.

FIG. 13 is a bottom plan view of the embodiment of FIG. 11.

FIG. 14 is a side elevation view of the embodiment of FIG. 11.

FIG. 15 is an exploded view of the embodiment of FIG. 11.

FIG. 16 is another exploded view of the embodiment of FIG. 11illustrating further details of its sensors and magnets.

FIG. 17 is an exploded top plan view of the embodiment of FIG. 11.

FIG. 18 is a sectional view of the embodiment of FIG. 11 taken alongline 18-18 of FIG. 17.

FIG. 19 is a schematic block diagram illustrating the relationshipbetween an individual magnet and the three-axis magnetic sensor utilizedin the embodiments of FIGS. 1 and 11.

FIG. 20 is a block diagram illustrating details of an embodiment of aprocess for integrating data from a typical magnetic sensor such as isshown in the embodiments of FIGS. 1 and 11.

FIG. 21 is a block diagram illustrating details of one embodiment of thepresent disclosure for use in communicating data to one or more remoteservers in accordance with aspects of the present disclosure.

FIG. 22 is a flow chart illustrating details of an embodiment of aprocess for integrating sensor data in accordance with aspects of thepresent disclosure.

FIG. 23 is a graph illustrating example X and Y sensor outputs from anon-board accelerometer embodiment which may be used in differentiatingground surface types in accordance with aspects of the presentdisclosure.

FIG. 24 is a graph illustrating example X and Y sensor outputs for theaccelerometer embodiment of FIG. 23, at two different scales.

FIG. 25 illustrates details an embodiment of a ground tracking devicewith incorporated sondes in accordance with aspects of the presentdisclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

The present disclosure relates generally to systems, methods, andapparatus for locating buried objects. Objects for locating buriedobjects are denoted herein as “locators.” More specifically, but notexclusively, the disclosure relates to ground tracking devices forattachment to locators or other measurement devices to follow a groundor other surface and provide position and/or motion information inmultiple axes of motion.

For example, in one aspect, the disclosure relates to a ground trackingdevice. The ground tracking device may include a ground followerassembly, and a mounting assembly configured to floatably attach theground follower assembly to a measurement device. The ground followerassembly may be configured to generate one or more output signalsrepresentative of a motion of the measurement device over a groundsurface in two or more axes or dimensions of motion.

The mounting apparatus may, for example, be configured to detachedlymount the ground follower assembly to the measurement device. Themeasurement device may be a portable locator device or other test ormeasurement instrument or device. The ground follower assembly mayinclude a yoke element and a swing-arm element, and the mountingassembly may include a bracket assembly configured to detachably connectthe yoke element to the measurement device.

The ground follower assembly may include, for example, a ground followerelement, a swing-arm element coupled to the ground follower element, ayoke element coupled between the swing-arm element and the mountingassembly, and a plurality of sensors configured to sense movement of theground follower assembly relative to a ground surface or other surfacein two or more axes of motion and generate the one or more outputsignals based at least in part on the sensed movement. The plurality ofsensors may include, for example, magnetic sensors, and the groundfollower assembly may further include a corresponding plurality ofmagnets. The magnetic sensors may be three-axis magnetic sensors.

The ground follower element may include, for example, a wheel, and theyoke may be a C-shaped yoke. Alternately, the ground follower elementmay include two or more wheels. Alternately, the ground follower elementmay include a sphere or other ground tracking element or device.

The ground tracking device may further include, for example, a surfacesensing apparatus. The surface sensor apparatus may be configured toprovide a signal usable to determine a ground surface characteristic.The surface sensing apparatus may include a ground surface sensorconfigured to sense light reflected from the ground or other surface andprovide a ground surface output signal associated with a surfacecharacteristic. The surface sensing apparatus may further include alighting element configured to generate a light output directed at theground surface, and the ground surface sensor is configured to generatethe ground surface output based at least in part on reflection of thelight output from the ground surface. The ground surface sensor may bean optical sensor. The ground surface sensor may be a single sensor. Theoptical sensor may be a linear row of pixel sensors or a grid of pixelsensors. The ground surface sensor may be a camera element, such as adigital camera sensor element. The lighting element may be a lightemitting diode (LED) or other lighting element. The light emittingelement may include a white LED. The light emitting element may includeLEDs or other lighting elements of specific wavelengths or ranges ofwavelengths. The wavelengths may be selected based on a ground orsurface characteristic, such as light absorption or reflectivity. Thelight emitting element may include an array of LEDs or other lightemitting devices. The ground tracking device may further include acircuit configured to determine, based at least in part on the outputsignal from the ground surface sensor, a ground type.

The motion of the measurement device to be sensed may include, forexample, a rotational motion about a substantially fixed groundreference point, and the one or more output signals may include one ormore signals corresponding to the rotational motion about thesubstantially fixed ground point. Alternately, or in addition, themotion of the measuring device to be sensed may include an up or downmotion of the ground tracking device about the ground surface, and theone or more signals may include one or more signals corresponding to theup or down motion. Alternately, or in addition, the motion of themeasuring device may include a side-to-side motion and the one or moresignals include one or more signals corresponding to the side-to-sidemotion. Alternately, or in addition, the motion of the measurementdevice to be sensed may include a translational motion over the groundsurface, and the one or more signals may include one or more signalscorresponding to the translational motion.

The ground tracking device may further include, for example, a compassdevice. The compass device may be configured to generate a compassoutput signal corresponding to a position of the ground followerassembly. The ground tracking device may further include anaccelerometer. The accelerometer may be configured to generate anaccelerometer output signal corresponding to a motion of the groundfollower assembly. The ground tracking device may further include asensor apparatus configured to sense a rotation of one or more wheelsassociated with translation motion of the measurement device. The groundtracking device may further include a GPS receiver module or otherterrestrial or satellite position location device.

The motion of the measurement device to be sensed may include, forexample, a rotational motion about a substantially fixed groundreference point, and the one or more output signals may include one ormore signals corresponding to the rotational motion about thesubstantially fixed ground point; an up or down motion of the groundtracking device about the ground surface, and the one or more signalsinclude one or more signals corresponding to the up or down motion; anda side-to-side motion and the one or more signals include one or moresignals corresponding to the side-to-side motion. The motion of themeasurement device to be sensed may further includes a translationalmotion over the ground surface, and the one or more signals furtherinclude one or more signals corresponding to the translational motion.

The ground tracking device may further include, for example, one or moreSondes coupled to a ground follower element such as one or more wheels.The ground tracking device may include ones of a plurality of Sondescoupled to ones of a plurality of wheels.

In another aspect, the disclosure relates to a ground tracking device.The ground tracking device may include, for example, a wheel, a wheelsensor element configured to measure a rotation of the wheel andgenerate a wheel rotation output signal corresponding to the rotation ofthe wheel, a swing arm assembly coupled at a first end to the wheelassembly, a yoke assembly coupled at a second end of the swing armassembly, a swing arm sensor element configured to sense a rotary motionof the second end of the swing arm assembly and generate a swing armrotation output signal corresponding to the rotary motion of the swingarm assembly, and a yoke sensor element configured to sense a rotationof the yoke assembly relative to a centerline of a measurement deviceand generate a yoke rotation signal corresponding to the rotation of theyoke assembly.

In another aspect, the disclosure relates to a dual wheel groundtracking device. The ground tracking device may include, for example, awheel arm structure assembly, a first wheel coupled to the wheel armstructure assembly, a first wheel sensor element configured to measure arotation of the first wheel and generate a first wheel rotation outputsignal corresponding to the rotation of the first wheel, a second wheelcoupled to the wheel arm structure assembly and the first wheel, asecond wheel sensor element configured to measure a rotation of thesecond wheel and generate a second wheel rotation output signalcorresponding to the rotation of the second wheel, a yoke assembly, awrist joint assembly coupled between the wheel arm structure assemblyand the yoke assembly, a yoke sensor element configured to sense arotation of the yoke assembly relative to a centerline of a measurementdevice and generate a yoke rotation signal corresponding to the rotationof the yoke assembly, and a wrist joint sensor element configured tosense a movement of the wheel arm structure assembly relative to theyoke assembly and generate a wheel arm movement signal corresponding tothe movement of the wheel arm structure assembly relative to the yokeassembly.

In another aspect, the disclosure relates to a ground tracking locatorsystem. The ground tracker locator system may include a portable locatorand a ground tracking device. The ground tracking device may include aground follower assembly, and a mounting assembly configured tofloatably attach the ground follower assembly to the portable locator.The ground follower assembly may be configured to generate one or moreoutput signals representative of a motion of the locator device over aground surface in two or more axes or dimensions of motion.

Various embodiments of the present disclosure may be used or combinedwith buried object locators and associated devices, such as sondes. Forexample, various ground tracking device embodiments may be combined withlocators and sondes such as are described in U.S. Pat. No. 7,009,399,entitled OMNIDIRECTIONAL SONDE AND LINE LOCATOR, issued Mar. 7, 2006; inU.S. Pat. No. 7,332,901, entitled LOCATOR WITH APPARENT DEPTHINDICATION, issued Feb. 19, 2008; U.S. Pat. No. 7,336,078, entitledMULTI-SENSOR MAPPING OMNIDIRECTIONAL SONDE AND LINE LOCATORS, issuedFeb. 26, 2008; U.S. Pat. No. 7,443,154, entitled MULTI-SENSOR MAPPINGOMNIDIRECTIONAL SONDE AND LINE LOCATOR, issued Oct. 28, 2008; U.S. Pat.No. 7,619,516, entitled SINGLE AND MULTI-TRACE OMNIDIRECTIONAL SONDE ANDLINE LOCATORS AND TRANSMITTER USED THEREWITH, issued Nov. 17, 2009; U.S.Pat. No. 7,733,077, entitled MULTI-SENSOR MAPPING OMNIDIRECTIONAL SONDEAND LINE LOCATORS AND TRANSMITTER USED THEREWITH, issued Jun. 8, 2010;U.S. Pat. No. 7,741,848, entitled ADAPTIVE MULTICHANNEL LOCATOR SYSTEMFOR MULTIPLE PROXIMITY DETECTION, issued Jun. 22, 2010; U.S. Pat. No.7,755,360, entitled PORTABLE LOCATOR SYSTEM WITH JAMMING REDUCTION,issued Jul. 13, 2010; U.S. Pat. No. 7,825,647, entitled METHOD FORLOCATING BURIED PIPES AND CABLES, issued Nov. 2, 2010; U.S. Pat. No.7,830,149, entitled AN UNDERGROUND UTILITY LOCATOR WITH A TRANSMITTER, APAIR OF UPWARDLY OPENING POCKETS AND HELICAL COIL TYPE ELECTRICAL CORDS,issued Nov. 9, 2010; as well as in U.S. Patent Publication 2011/0006772,entitled TRI-POD BURIED LOCATOR SYSTEM, published Jan. 13, 2011(collectively referred to herein as the “related applications”). Thecontent of each of these applications is incorporated by referenceherein in its entirety.

The term “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect and/or embodiment describedherein as “exemplary” is not necessarily to be construed as preferred oradvantageous over other aspects and/or embodiments.

Overview

The ability to perform reliable mapping while locating buried objectscan provide various advantages. For example, mapping can be combinedwith locating results to record, store, and re-use the results ofprevious locating tasks, known as “locates,” as well as reducingunnecessary repetitive visits to the same site. Operators can improvethe accuracy of locates, as well as improve the ability to revisit andre-mark utilities more rapidly for later excavation, by accuratelyrelating them to surface positions and features. Other potentialadvantages of reliable mapping may include speed improvement, accuracyimprovement, cost reductions, and/or other advantages.

Various embodiments of the present disclosure may be used to facilitateintegration of mapping and imagery data with information collected by aburied object locator. This may be done by, for example, measuringmovement information to reduce the variability of positional data andinformation of a hand-held locator relative to a ground surface or othersurface or position of the locator (relative to a reference point orsurface), such as described subsequently herein.

In traditional locating, a hand-held locating device is held at anindeterminate and variable distance above the ground's surface as anoperator/user walks along the path of a detected signal (typicallyassociated with the buried object, such as a pipe or cable). Forexample, a user may trace a buried power cable by measuringelectromagnetic signals generated by the conductor, or may locate ortrace signals generated by sondes. In operation, the locator is oftenswung from side to side to attempt to determine the maximum signal fromthe buried utility. This introduces user-induced variability inmeasurement and position determination. This user-induced variabilitymay become compounded in situations where a traced signal becomesdistorted or ambiguous due to signal dissipation, bleed-through fromother conductors, and/or due to other factors, such as electromagneticdistortions, interference from other signals, buried utility pathchanges or branches, etc.

In order to facilitate better locates, accurate recording of theposition of a locating device from moment to moment in multiple axes,such as two or three axes (X, Y and/or Z) relative to ground or surfacepositions, as well as rotational orientation around axes X, Y and Z,side-to-side movements, and/or other movements may be used. Althoughsimple wheel-based counters have been used to measure distance traveled,this measurement approach is limited to providing an approximatelylinear measurement from a known starting point or position. Traditionalwheel-based counters cannot, however, provide measurement laterally orvertically (Y and Z), and they ignore rotational orientation around thethree axes (e.g., axes in X, Y, and Z dimensions).

In addition, the accuracy of computed depth readings of buriedconductors by modern locating devices may be improved by determining anaccurate value for the height above ground of the antenna used indetecting the conductor. In the absence of measurement of the relativeheight above ground of the locator, such computation must depend onestimates and approximation.

Various embodiments of the present disclosure may be used to provide animproved ground-tracking device capable of capturing positional and/ororientation information of an associated utility locator in multipledimensions and axes of motion. The illustrated embodiments are generallyconfigured for use with an appropriately constructed locator, such asthose illustrated in the related applications, in which the lowerantenna enclosure is optionally fitted with an accessory port. However,other configurations of locators or other attached devices may also beused within the spirit and scope of the present invention.

The illustrated embodiments may be integrated with sensors includingaccelerometers, such as a three-axis accelerometer integrated circuit(IC), compass devices, such as a three-axis compass IC, gyroscopicdevices, such as a three-axis gyroscopic sensor IC, microprocessors,microcontrollers, ASICs, FPGAs, and/or other programmable devices,and/or satellite locations systems, such as a GPS receiving chip ormodule. The data from these sensors may be integrated with outputs froma set of rotational motion sensors, such as multi-axis magnetic sensors,to measure the angles of permanent magnets located at rotating joints ofthe ground tracking device, to provide data or information associatedwith movement of the locator about various axes of motion.

In addition, a surface sensing apparatus may be included to sense acharacteristic of the ground or other surface adjacent to the locatorand ground tracking device. For example, the surface sensing apparatusmay be configured to sense the type of ground over which the locator isbeing moved, such as dirt, macadam, concrete, grass, or other surfaces.This may be done by using, for example, a light emitting element and/oran associated ground surface sensor, which may be a light sensor. In oneembodiment, the light emitting element may be an LED emitter disposed toemit light at a wavelength or range of wavelengths suitable for surfacedetection. In one embodiment, the surface sensing element may be acamera or color sensor array with an associated white LED emitter whichmay be used to measure ground color and use this to determine variousground surfaces. By providing controlled light to the surface, thesensor array element may then detect reflected and/or ambient light andprovide an output that may be used to determine a surface type, such asbased on color and/or texture. An output signal from the ground surfacesensor may be further processed to determine a surface characteristic,such as a surface color or texture. This may be used to determine asurface type, such as grass, concrete, dirt, macadam, or other surfaces.

Other sensor elements may also be used in various embodiments. Forexample, a laser altimeter or an acoustic altimeter may be incorporatedfor continuous acquisition of height-above-ground data during a locateoperation. This may be combined with other motion sensing elements suchas described subsequently herein to provide additional measurement data.

Example Ground Tracking Device Embodiments

Referring to FIG. 1A, an example ground tracking system 100 includes ameasurement device, such as a portable locator 104, to track the path ofa buried conductor 106 onto which an electromagnetic signal 108 of aknown frequency has been actively imposed by a transmitter or sonde (notillustrated), or alternatively which carries an electromagnetic signalthat can be passively detected by the locator 104, such as a signalgenerated by a current in a buried electrical power transmission cable.Examples of portable locators include battery powered man portableutility locators such as those described in the related applications,including exemplary locator devices as described in U.S. Pat. No.7,009,399, entitled OMNIDIRECTIONAL SONDE AND LINE LOCATOR, issued Mar.7, 2006; U.S. Pat. No. 7,332,091, entitled PROCESS FOR TREATING STORMWATER, issued Feb. 19, 2008; and U.S. Pat. No. 7,733,077, entitledMULTI-SENSOR MAPPING OMNIDIRECTIONAL SONDE AND LINE LOCATORS ANDTRANSMITTER USED THEREWITH, issued Jun. 8, 2010. The content of each ofthese applications is hereby incorporated by reference herein in itsentirety for all purposes. Although the example system 100 shown in FIG.1A is illustrated and described with respect to a particular type ofburied object locator as shown, it will be apparent that the groundtracking device embodiments as shown and described subsequently hereinmay be adapted to be used with other types of test and measurementsdevices in addition to the specific buried object locator shown.

In a typical ground tracking system 100, a ground tracking device, suchas the ground tracking device embodiment 110 shown in FIGS. 1A and 2(comprising a ground follower assembly including the wheel 116, swingarm 132, yoke 112, sensing elements associated with these elements, aswell as associated mechanical and electronic components, and a mountingassembly including brackets 128 and 130) may be attached to a locator104 to follow the ground or other surfaces and provide sensed data withrespect to multiple positions and movements of the locator 104 relativeto the ground or other surface. Various other embodiments of groundtracking devices may be used in different implementations, such as thesingle wheel embodiments shown in FIGS. 1A and 2, the dual wheelembodiment shown in FIGS. 11 and 12, or other embodiments, such as thespheroid embodiment shown in FIG. 1E.

In the exemplary embodiment shown in FIG. 1A, the ground followerassembly includes a ground follower element, such as wheel 116,associated sensor elements to detect position and/or motion about two ormore axes of motion of the ground follower assembly, as well asfloatable elements, such as one or more yokes, along with associatedelements, such as bearings and related elements to couple the groundfollower assembly to the mounting assembly. Other ground followerassembly embodiments may include multiple wheels as ground followers,and/or other ground follower elements, such as the spheroid element 350shown in FIG. 1E. In operation, the ground tracking device is configuredto follow a ground surface 300 through contact between the groundfollower element and the ground or other surface and generate signalscorresponding to position and/or motion of the attached measurementdevice, such as locator 104, over and/or relative to the ground surfacein two or more axes or directions of motion.

For example, FIG. 1B illustrates one type of motion of a locator 104 andattached ground tracking device, such as ground tracking device 110,relative to a substantially fixed reference point on the ground or othersurface. In this example, shown as a top or bird's eye view looking downon the locator 104 and ground tracking device 110, the ground or othersurface being followed may be defined by X and Y axes as shown. Anoperator (not shown) may rotate the locator about a substantially fixedreference point 310 in the X-Y plane (i.e. on the ground or othersurface), with the ground tracking device providing data or informationfor use in measuring the position and/or motion of the locator about thereference point 310. In operation, the operator may start themeasurement process as shown in orientation 100B-1 at Position 1, andthen rotate the locator through an angle such as angle Φ1 or Φ2 as shownto new orientations 100B-2 (Position 2) or 100B-3 (Position 3),respectively. This rotational motion may be sensed and a correspondingoutput signal generated. Yoke sensor element configurations, such asdescribed subsequently herein, may be used to sense this motion.

The associated position and/or motion of the locator 104 may bedetermined at least in part from output signals provided from the groundtracking device, such as by sensing positions and/or movements in X andY axes and/or angular rotations such as Φ1 or Φ2 and generatingcorresponding signals (which may correspond to motion 118 as shown inFIG. 1A or motion 200 as shown in FIG. 11). In the embodiment shown,wheel 116 will typically pivot somewhat about reference point 310 andmay move slightly in the X and Y dimensions. In other embodiments, suchas the two-wheel embodiment shown in FIGS. 11 and 12, the two wheels 212and 214 may rotate in opposite directions during movements as shown inFIG. 1D (where reference point 310 is located between the two wheels),which may minimize displacement of the ground tracking device from thereference point 310.

FIG. 1C illustrates up/down elevation movements that may be sensed by aground tracking device such as shown in FIG. 1A. These rotationalmotions may be sensed by a sensor element and a corresponding outputsignal may be generated. Swing arm sensor configurations as describedsubsequently herein may be used to sense this motion. In orientation100C-1, the locator 104 (where a lower antenna ball is a referenceposition on the locator device) is positioned at a bottom positionrelative to the ground surface 300. In this position, the angle Θ1between a swing arm assembly of the ground tracking device 110 isapproximately 90 degrees from the locator mast and may be sensed todetermine the elevation, E1, of the locator in an up-down orientation(elevation in a Z dimension) relative to the ground surface 300. Acorresponding distance D1 from the ground follower element (in thisembodiment, wheel 116) may also be determined. Similarly, inorientations 100C-2 and 100C-3, respective angles Θ2 and Θ3 may bemeasured to determine corresponding heights or elevations E2 and E3 ofthe locator 104 above the ground surface 300.

FIG. 1D illustrates an example of side-to-side movements that maylikewise be measured in some embodiments. As shown in FIG. 1D, a twowheel ground follower assembly may be better suited for determiningside-to-side measurements, which may be determined based on measurementof angles such as β1, β2, or β3.

Although the embodiments shown in FIG. 1A and FIG. 11 include wheels,such as wheel 116 or wheels 212 and 214, in the ground followerassembly, in some embodiments other ground following elements may beused. For example, FIG. 1E illustrates one embodiment using a spheroidground following element 350 to follow the ground surface 300. Inembodiments using wheels or similar elements, one or more wheels ofdifferent widths, diameters, and/or numbers may be used, and the wheelsmay be configured with treads of varying widths and shapes, such astreads curved or otherwise shaped to follow the ground or other targetedsurfaces. Some embodiments may use other mechanical elements andassociated sensors to follow the ground and provide motion signalscorresponding to motions such as those shown in FIGS. 1B, 1C, and 1D toan attached measurement device, such as locator 104. For example, someembodiments may use extended arms, pointers, or other apparatus tosubstantially follow a ground surface or other surface during a buriedobject tracing or other measurement process.

Returning to FIG. 1A, in an exemplary embodiment, ground tracking device110 includes a ground follower assembly including a wheel 116, and ayoke 112, which may be in a C-shape configuration as shown and/or inother similar or equivalent configurations. The ground tracking device110 may be coupled to a mast 120 of the locator as shown.

In the embodiment shown in FIG. 1A, the ground tracking device 110 hasfreedom of motion around multiple axes of motion or pivot points,including a rotary motion 114 around the axle of wheel 116 to providesensing of directional or translational motion along the ground or othersurface; a rotary motion 118, corresponding to the movements illustratedin FIG. 1B in X and Y dimensions, around a vertical axis of the locator104, such as about the vertical mast 120 or other measurement devicecenterline, which may be implemented by a C-shaped yoke mechanism 112(or other similar or equivalent mechanism); as well as a rotary motion122 of a connecting arm assembly, corresponding to the up/down motion orelevation in a Z dimension, as shown in FIG. 1C, which may beimplemented using a yoke joint assembly 124 positioned at the midsectionof the C-shaped yoke 112 (or via other mechanisms to effect similarup/down movements as shown in FIG. 1C). Typical measurement devicemovements may include combinations of two or more movements.

For each of these degrees of freedom of motion, signals and/or datacorresponding to positions and/or movements of the locator 104 (or othermeasurement device) in the various axes or dimensions of motion may begenerated by sensors configured to measure the corresponding movements.The sensed signals may be measured in X, Y and Z dimensions anddistances and/or in angular measurements, or in combinations of both.The sensed signals may be analog or digital signals in variousembodiments.

In an exemplary embodiment, sensors may be located approximately at eachpivot point, such as that shown in FIG. 5, to generate position and/ormotion signals. The sensed signals may then be processed in ameasurement circuit (not shown) in the ground tracking device, withprocessed output signals then provided to the locator 104. In someembodiments, the sensed motion signals may be processed in whole or inpart in the measurement circuit, with processed data or information sentto the locator 104. However, in other embodiments the sensed motionsignals may be provided directly from the ground tracking device to themeasurement device and processed in the measurement device.

The measured motion signals corresponding to the various axes of motionmay then be used to calculate and map position, motion, location,orientation, and/or terrain data or information associated withmovements of locator 104 by operator 102. Signals provided from theground tracking device may be combined or processed in combination withadditional signals provided from the locator to generate the positionand/or movement data as well as to generate mapping data for thelocating or tracing procedure. For example, accelerometer or othermotion sensing devices in a locator may be combined with motion signalsfrom the ground tracking device to distinguish relative movementsassociated with the locator from movements generated by sensors in theground tracking device. This can be used to generate more completemapping data reflecting position and movements of the combinedlocator/ground tracking device (or other measurement instrumentscombined with a corresponding ground tracking device). The data may bestored in the ground tracking device and/or locator or other instrumentfor subsequent download and/or processing, such as in a separatecomputer system.

In an exemplary embodiment, the sensors may comprise magnetic sensorsand associated permanent magnets to generate position and/or motionsignals. However, in some embodiments optical encoders, potentiometers,gyroscopic devices, compass devices, and/or other sensor elements andassociated hardware and signal processing circuits may be used to senserelative position and motion, such as described subsequently herein.

Referring to FIG. 2, additional details of the embodiment of FIG. 1 areillustrated. As shown in FIG. 1, an exemplary locator such as locator104 may have a spherical lower antenna enclosure 126 secured to acylindrical locator mast 120. A yoke mechanism, such as C-shaped yoke112, may be secured around the locator mast 120 above the lower antennaenclosure 126 and may be further coupled to the bottom of the lowerantenna enclosure 126 or to other lower measurement device structures.The yoke 112 may be configured in an approximately C-shapedconfiguration and may be coupled to the locator mast 120 (or othersimilar or equivalent structures of other locators or measurementdevices) by a mounting assembly, which may include a left yoke bracket128 and a right yoke bracket 130, or other mounting apparatus. In anexemplary embodiment, the mounting assembly may be detachable so thatthe ground tracking device may be readily attached or removed from themeasurement device; however, in some embodiments the measurement deviceand ground tracking device may be coupled in a more fixed configuration.

To facilitate movements such as those shown in FIG. 1B, the C-shapedyoke 112 may be configured so as to freely rotate around the verticalaxis of the locator mast 120 and of the lower antenna enclosure 126, orabout another centerline of a measurement device. A yoke sensor may beused to sense this motion.

In the exemplary embodiment illustrated, at the midsection of theC-shaped yoke 112, a yoke joint assembly 124 may be formed to which aswing arm assembly, such as swing arm structure 132, may be attached.The swing arm assembly may include one or more arm elements or otherfloatable supporting elements. In an exemplary embodiment, the swing armassembly includes a right arm half 134 and a left arm half 136, operablycoupled such that the swing arm structure 132 provides a floating linkthat rotates around the horizontal axis of the yoke joint assembly 124.However, other configurations may include single arms or other elementsto floatably couple a wheel or other ground tracking element. The leftarm half 136 may be covered by a left plastic arm cap 138, and the rightarm half 134 may be covered by a right plastic arm cap 140. The armstructure 132 may also incorporate an intermediate supporting structure,such as molded mounting block 142, to provide rigidity and structuralstrength to the arm structure 132.

FIG. 2 shows ground tracking device 110 rotated into a verticalalignment with locator 104 (for purposes of illustration). However, intypical use, ground tracking device 104 would be operated atapproximately a ninety-degree angle to the locator 104, as illustratedin FIG. 1A, and may be moved in the various motions as shown in FIG. 1B,FIG. 1C, and/or FIG. 1D during operation. For example, if the locator104 is lifted to clear an obstacle, the ground tracking device 110 willmove into a nearly vertical position as illustrated in FIG. 2. Thevertical configuration shown in FIG. 2 may also be used for storage,etc., and a locking mechanism (not shown) may be included to lock theground tracking device 110 into a locked position relative to thelocator 104.

At the lower end of the arm structure 132 a wheel hub assembly 144 maybe used to provide a wheel bearing axle 146 (illustrated in FIG. 5, butobscured in FIG. 2 by axle bushing 147) to facilitate rotation of wheel116. The wheel 116 may rotate around a central axis of the wheel hubassembly 144. Rotational motion of the wheel 116 about the central axismay be sensed by a wheel sensor element and used to generate signalsand/or data corresponding to movement of the wheel across the ground orother surface.

FIG. 3 and FIG. 4 illustrate example pivot points and theircorresponding degrees of freedom for the exemplary ground trackingdevice embodiment 110. FIG. 3 illustrates a view of the ground trackingdevice 110 and locator 104 looking upward from below, such as would beseen looking upward from the ground during a locate operation. Therotary motion 118 illustrates rotation of the ground tracking device 110around a vertical axis of the lower antenna enclosure 126 and thelocator mast 120 (as shown in FIGS. 1A and 2), such as is shown in theexample movements of FIG. 1B. The rotary motion 114 indicates the rotarymotion around the axle of the wheel 116, such as when the wheel is beingrolled across the ground or other surface. The rotary motion 122indicates a vertical rotation of the ground tracking device 110 aroundthe horizontal axis of the yoke joint assembly 124, such as tofacilitate the up/down elevation motion as shown in FIG. 1C.

In some embodiments, a surface sensing apparatus may be included tosense the type of ground or other surface over which the measurementdevice and ground tracking device are being moved. For example, in anexemplary embodiment a lighting element and ground sensor element may bemounted on the ground tracking device, such as on a lower surface ofmounting block 142 as shown. The lighting element may be, for example, awhite LED 148, which may be mounted adjacent to an optical sensor 150.The optical sensor may be, for example, a single-pixel optical sensor(four sub-pixels) device such as the Avago ADJD-S311-CR999 RGB colorsensor. Alternately, optical sensors with other pixel configurations,such as a sensor with four pixels (16 sub-pixels) such as the TAOSTCS3404 or 3414 may be used. In some cases, the sensor element may bepassively configured so that no specific lighting element is used andthe sensor processes ambient light. In various configurations, othertypes of lighting elements and sensors may be used, such as lightingelements and sensors operating in various visible light, infra-red,ultra-violet, or at other wavelengths. Other sensor devices capable ofmeasuring a characteristic of the ground or other surface mayalternately be used, such as, for example, acoustic sensors.

In operation, the lighting element and sensor may be configured toprovide simple color differentiation among ground types. For example,the white LED 148 and the optical sensor 150 may be mounted on an insetoptical sensor printed circuit board (PCB) 152. In operation the whiteLED 148 strobes or energizes a white light, either continuously during alocate or tracking operation or at fixed or varying time intervals. Theoptical sensor 150 generates a signal or data based on received lightthat is reflected from the ground surface. Signals or data generated bythe optical sensor 150 may then be processed to make a determination asto the type of different surfaces (e.g, grass, asphalt or macadam,concrete, dirt, etc.). The determination may be based on, for example,detection of color, texture, or other characteristics of the surface. Inaddition, other characteristics, such as color marks, lines or othermarkings, such as spray-painted marks, etc., may be detected by thesurface sensing apparatus and may be stored and/or combined with othersensed data or information to improve mapping.

For example, in one embodiment, the surface determination data orinformation may be used to improve the accuracy of correlation betweenlocator detections in various positions and photographs or other imaginginformation, such as digitized maps or aerial images, in which surfacecolors are visible or are otherwise identified. It another aspect,surface determination data may be used to allow the locator to identifya particular color of a paint marking that has been applied to theground or other surface to correlate with water pipes, electric lines,cable TV cables, etc. (e.g., where color-coded marks are used toidentify various utilities). In some embodiments, optional opticalcontrol elements (not illustrated) may be used to control the field ofview of the sensor, such as optical sensor 150, and/or the output power,beam angle, emitted light wavelength, and/or other characteristics ofthe lighting element (such as white LED 148).

In some embodiments, the sensor may be a camera/photo sensor, such as adigital camera device which enables more complex ground patternrecognition. For example, if an image sensor such as a VGA or higherresolution sensor is used, features such as edge recognition, shapedetection, image integration, and/or other image processing functionsmay be implemented, such as through use of a feature transformphoto-stitching algorithm, edge or shape detection algorithm, or otherimage processing algorithm.

Referring to FIG. 5, the C-shaped yoke 112 may be secured around thelocator mast 120 above the lower antenna enclosure 126 using brackets,such as left yoke bracket 128 and yoke bracket 130 and a set of screwssuch as screws 154, or via other attachment mechanism. The lower antennaenclosure 126 of the locator 104 (FIG. 1) may be configured with anouter shell consisting of an upper shell half 156 and a lower shell half158 as shown. An adaptor port 160 (partially obscured in FIG. 5) may bemolded into the bottom of the lower shell half 158 in alignment with thevertical axis of the lower antenna enclosure 126 and the locator mast120. However, in some embodiments, different attachment mechanismsconfigured to removably or fixedly attach the ground tracking device tothe locator or other measurement device may be used.

In an exemplary embodiment, at each pivot point of the ground trackingdevice 110 (as shown in FIG. 1) a magnetically permeable magnetic shield162 and a permanent magnet 164 associated with the pivot point may belocated on one of the joined components. For example, an instance of themagnetic shield 162 and the permanent magnet 164 may be located embeddedwithin the molded adaptor port 160 as shown. The magnetic shield 162 andthe permanent magnet 164 associated with the wheel hub assembly 144 (asseen in FIG. 2) may be located in the molded center of a bushing 147seated on the right side of the wheel bearing 146 of the wheel 116 andfixed relative to the wheel 116. A magnetic shield 162 and permanentmagnet 164 associated with the yoke joint assembly 124 may be seated inthe bushing 147 of the right side of the yoke joint assembly 124, andmay be centrally aligned with the axis of the yoke joint assembly 124,fixed relative to the C-shaped yoke 112. Multiple magnetic shields 162may be used to prevent the magnetic field of associated permanentmagnets 164 from interfering with the detection of the electromagneticsignal 108 (as shown in FIG. 1) being transmitted from the buried object(such as the buried conductor 106 of FIG. 1).

The permanent magnets 164 and the magnetic shields 162 may be mountedon-axis at the pivot points to facilitate motion sensing. For example, athree-axis magnetic sensor 168 (such as the single die version of aMelexis MLX90333 sensor, for example) may be attached to a printedcircuit board and backed with foil shielding tape. The magnetic sensormay be mounted in close proximity to a corresponding magnet, but on theother component of each joint. Further details regarding the exampleMelexis MLX90333 sensor may be found in U.S. patent application Ser. No.12/756,068 entitled MAGNETIC MANUAL USER INTERFACE DEVICES, filed Apr.7, 2010. The content of this application is hereby incorporated byreference herein in its entirety for all purposes. Additional detailsare also shown in FIG. 19.

One or more magnetic sensors 168 may be associated with the adapter port160 and may be mounted on a sensor PCB 170 at the center of a moldedreceptacle 172 in the lower arm of the C-shaped yoke 112, fixed relativeto the C-shaped yoke 112. This magnet and sensor may be used tofacilitate sensing of fixed ground point rotation motions, such as thoseillustrated in FIG. 1B. The sensor PCB 170 may be backed by a layer ofmetallic foil backing 174 for additional shielding.

One or more magnetic sensors 168 corresponding to the magnets 164associated with the wheel hub assembly 144 (as shown in FIG. 2) and theyoke joint assembly 124 may be mounted on an arm PCB assembly 176, oneexample of which is further illustrated in detail in FIG. 6. This magnetand sensor configuration may be used to sense rolling motion of theground tracking device across the ground or other surface. A strip ofmetallic foil backing 178 may be attached adhesively to the back of thearm PCB assembly 176 to provide additional magnetic shielding.

In an exemplary embodiment, each of the permanent magnets 164 may beprecisely keyed in its polar orientation relative to the X, Y and Z axesof the ground tracking device 110 (as shown in FIG. 1). Exampleillustrations of the relationship between the magnetic shields 162, thepermanent magnets 164, and the magnetic sensors 168 are detailed inFIGS. 9 and 10. In this configuration, angles measured by the magneticsensors 168 may be measured continuously or periodically (e.g., sampled)to enable determination of motion over the ground, orientation, andheight above ground for the locator 104 (or other measurement device).Each instance of the magnetic shield 162 may contain an embeddedpermanent magnet 164, which may be rectangular in shape in an exemplaryembodiment. The permanent magnet 164 may be situated within the magneticshield 162 so that its dipole axis centerline precisely aligns with theaxis of rotation of its corresponding joint.

Referring to FIG. 6, the arm PCB assembly 176 may include an arm PCB 180on which a plurality of sensors may be mounted. These may include amagnetic sensor 168 associated with a permanent magnet 164 for sensingat the yoke joint assembly 124 (as shown in FIG. 5) and a magneticsensor 168 associated with a permanent magnet 164 for sensing at thewheel 116 (as shown in FIG. 5). The arm PCB 180 may optionally mount aprocessor element, such as a microcontroller 182 or other programmableprocessing element, a gyroscopic sensor device, such as a three-axisgyroscopic sensor IC 184, a satellite position sensing device, such as aGPS module 186, a compass device, such as three-axis compass IC 188, aswell as an accelerometer, such as a three-axis accelerometer IC 190.Signals or data generated from the sensors mounted on the arm PCB 180,as well as other sensor described herein, may be integrated andprocessed by computing processing circuitry built into the locator 104(FIG. 1) or the microcontroller or other processor 182, or both. Thedata or information may then be sent to other computing devices forfurther integration and/or processing.

As shown in FIG. 7, a magnetic shield 162 and a permanent magnet 164associated with the wheel hub assembly 144 may be located at the rightend of the wheel hub assembly 144. A magnetic sensor 168 associated withthe wheel hub assembly may be mounted on the arm PCB 180 and may beseated in a formed well in the right arm half 134 as shown.

At the right end of the yoke joint assembly 124 (as seen in FIG. 7), apermanent magnet 164 associated with the yoke joint assembly 124 may beseated in a magnetic shield 162 associated with the yoke joint assembly124, and may be seated within the joint portion of the molded yoke 112as shown in FIG. 7. The yoke joint's magnetic sensor 168, which may bemounted on the arm PCB 180 (e.g., part of the arm PCB assembly 176), maybe seated within a formed well in the right arm half 134 below the rightplastic arm cap 140. Experimental results suggest that a distance ofapproximately 0.05 inches between the permanent magnets 164 and theirrespective magnetic sensors may provide optimal performance for theparticular configuration and elements shown; however, depending on thetypes of devices used and their configurations, other distances mayalternately be used in various embodiments.

Referring to FIG. 8, a lower antenna enclosure 126 mounted onto thelocator mast 120 may contain an adapter port 160 in which a magneticshield 162 and a permanent magnet 164 associated with the adaptor port160 may be seated. A lower arm of the C-shaped yoke 112 may include areceptacle 172 positioned directly below the adaptor port 160 in which amagnetic sensor 168 may be seated on sensor PCB 170. The magnetic sensor168 may be used to measures angles of the magnetic field of thepermanent magnet 164 as the yoke 112 moves around the vertical axis ofthe locator mast 120, corresponding to fixed point ground rotationmovements as illustrated in FIG. 1B.

Referring to FIG. 9 and FIG. 10, an embodiment of a sensor assembly 192for measuring certain motions of a ground tracking device is shown.Sensor assembly 192 includes a magnet, a shield, a sensor, a PCB, and afoil arrangement, where the magnet may comprise a permanent magnet 164,a magnetic shield 162, and a three-axis magnetic sensor 168. In FIG. 9,the magnetic shield 162 may be configured as a cylinder of approximately0.75 inches in diameter in which a cavity has been drilled for theinsertion of a permanent magnet, which may be configured as a flat,rectangular permanent magnet 164 as shown. The magnetic shield 162 maybe included to minimize magnetic interference generated from thepermanent magnet 164. The permanent magnet 164 may be retained withinthe cavity of the magnetic shield 162 by glue or other attachmentmechanisms. The magnetic sensor 168 may be mounted on the sensor PCB 170and may be located in alignment with the centerline of the permanentmagnet 164. The sensor PCB 170 may be backed with a layer of metallicfoil backing 174, such as a commercially available 80% nickel alloymagnetic shielding foil, for example, to provide further shielding. InFIG. 10 the same configuration of magnet, shield, sensor, PCB and foilarrangement as shown in FIG. 9 is illustrated from a side view,sectioned through the center width of the permanent magnet 164.

Wired, slip-ring, or wireless connections may be used to communicatesensor data to the locator 104 or to other processors or signalprocessing circuits. For example, processed or raw sensor signals ordata from the ground tracking device 110 may be transmitted to thelocator 104 or to another device, such as a smart phone, notebookcomputer, table device, or other similar or equivalent device by wiredor wireless mechanisms, such as via a USB interface, BlueTooth™ or otherwireless interface, or other wired or wireless connection. Adaptor port160 (as shown in FIG. 8) may include a slack wired loop or electricalslip ring assembly (not illustrated) to provide power and/or dataconnections between the locator 104 and ground tracking device 110. Anexample of one sling ring assembly that can be adapted for providing aplurality of conductive paths between the locator 104 and the groundtracking device 110 for transmitting data and power is described in U.S.Pat. No. 6,908,310, entitled SLIP RING ASSEMBLY WITH INTEGRAL POSITIONENCODER, issued Jun. 21, 2005. The content of this application is herebyincorporated by reference herein in its entirety for all purposes.Alternatively, a slack wire loop allowing partial rotation around thelocator mast 120 (as shown in FIG. 5), or an electrical slip ringassembly (not illustrated) may be used between the upper portion of theC-shaped yoke 112 and the locator mast 120 to allow continuousunrestricted rotation of the ground tracking device 110 around locatormast 120.

Ground tracking devices such as ground tracking device 110 may bebattery powered by an internal removable battery (not illustrated) ormay be powered by a battery in the locator 104, such as is shown in FIG.1A. Sensor data can be transmitted to an external remote device bysignal connection apparatus such as Wi-Fi, BlueTooth, IR, acoustic, orradio transmitters and receivers.

Some embodiments may include more than one wheel and multiple flexiblejoints or other movable connections in the ground follower assembly toimprove the travel of the ground tracking device over uneven terrainand/or provide additional sensor data or information. One suchembodiment is illustrated in FIG. 11, in which a dual-wheel groundtracking system 194 includes a locator, which may be same locator 104 asshown in FIG. 1, coupled to a dual-wheel ground tracking device 196,which may be moved across uneven terrain by an operator 102 but may beable to sense additional ground or surface characteristics. Examples ofmovements that may be sensed with a multi-wheel (or equivalent) groundtracking device embodiment, such as embodiment 196, are shown in FIG.1D, where the locator 104 may be moved in a side-to-side rotationrelative to the dual wheels, such as left wheel 212 and right wheel 214.

For example, in the orientation shown in illustration 100D-1, thelocator 104 is tilted an angle β1 with respect to the ground surface 300(in this example, at an angle slightly greater than 90 degrees from theground horizontal). A side-to-side sensor assembly in the groundtracking device 196, such as described subsequently, may be configuredto measure the side-to-side movement and generate and providecorresponding signals that may be processed in the ground trackingdevice and/or provided to the locator 104. Additional sensing elements,such as gyroscopic sensors, accelerometers, additional magnetic sensors,tilt sensors, or other sensing elements may be further used to generateadditional measurement information that may be combined with theside-to-side measurement data. For example, an accelerometer orgyroscopic sensor disposed in the locator 104 may generate signalscorresponding to the relative position or movement of the locator withrespect to vertical. This information may be combined with theside-to-side sensor information to generate further data and informationregarding a locate or tracking procedure.

For example, in the orientation shown in illustration 100D-2, thelocator is tilted to the right side of vertical (as shown in the figure)at an angle β2. In this position, the locator 104 is offset to the rightfrom vertical while the ground follower assembly (including wheels 212and 214) is in a vertical position. Alternately, in the orientationshown in illustration 100D-3, the locator is in a vertical position,while the ground follower assembly is offset from the vertical (e.g., atan angle β3), corresponding to a ground slope. By sensing theside-to-side rotation of the ground follower assembly as well as thevertical offset of the locator 104, a determination may be made as tothe slope or offset of the ground from horizontal (e.g., 90−β3 degreesin this case). The angles β2 and β3 may be the same; however, by sensingboth side-to-side rotation of the ground tracking device and verticalorientation of the locator, additional information about the locate ortracking procedure (e.g., whether the ground is level and the locator istilted to the side as shown in 100D-2, or whether the locator isvertical and the ground is sloped as shown in 100D-3, or combinations ofboth (not shown)) may be determined.

In some embodiments, vertical orientation sensing, such as describedabove with respect to the locator, may be incorporated in the groundtracking device. For example, in some embodiments a ground trackingdevice may include a gyroscope, accelerometer, tilt sensor, or othersensing element to further sense vertical orientation. In otherembodiments, vertical orientation sensing may be incorporated into thelocator or other measurement device. In addition, in some embodiments,vertical orientation sensing may be incorporated in both the groundtracking device and the locator or other measurement device.

Returning to the ground tracking device embodiment 196 shown in FIG. 12,a yoke 198 may be used to facilitate a rotation 200 (as shown in FIG. 11and corresponding to the movements shown in FIG. 1B) around the verticalaxis of the locator 104 (e.g., around locator mast 120 and lower antennaenclosure 126), with an associated yoke sensor configured to sense therotation and generate an output signal corresponding to the rotation. Ayoke joint 202 may be formed at the midsection of the yoke 198 to enablea rotation 204 around the horizontal axis of the yoke joint 202 tofacilitate movements such as shown in FIG. 1C. A wrist joint assembly,such as wrist joint assembly 206, may be used to enable a limited-travelrotation 208 clockwise or counter-clockwise (as viewed from the frontend of the dual-wheel ground tracking device 196) around a horizontalaxis through the center of the wrist joint assembly 206. This may beused to sense side-to-side motion as described previously herein.

Details of example wrist joint assembly embodiment 206 are further shownin FIG. 15. As noted previously, dual or multi-wheel ground followerassembly embodiments such as shown on ground tracking device 196 arealso capable of separate wheel rotations 210 around the wheel hub of aleft wheel 212 and a right wheel 214. These separate rotationalmovements may also be sensed to provide signals for generating furtherdata or information such as rotational direction, speed, etc.

The embodiment of FIG. 11 includes five instances of the magnet, shield,sensor, PCB and foil arrangement 192 (as shown in FIGS. 9 and 10), asthe left wheel 212, the right wheel 214, the yoke joint 202 and thewrist joint assembly 206, as well as rotation around the vertical axisof the locator mast 120 made possible by the yoke 198, may all moveindependently of each other as the dual-wheel ground tracking system 194is moved by the operator 102 across varying terrain. An exampleconfiguration of the various magnets 164, magnetic shields 162, andmagnetic sensors 168 is shown in FIGS. 15 and 16 in further detail.

An example configuration of the magnetic sensor 168, the magnetic shield162 and the permanent magnet 164 used to measure rotation around theaxis of the locator mast 120 in this embodiment is shown in FIG. 8.

Returning to FIG. 12, additional details of an embodiment of adual-wheel ground tracking device 196 is shown. In this embodiment, theground tracking device is moveably attached to the locator mast 120 bybrackets, including a left yoke bracket 128 and a right yoke bracket130, which may be secured by screws, such as screws 154 shown in FIG. 5,or using other attachment mechanisms. In some configurations, theattachment mechanism may be configured to quickly attach or detach, suchas by using latches, straps, or other removable attachment mechanisms.

In the illustrated embodiment, the yoke 198 is configured to rotatearound the locator mast 120. The yoke 198 may include a yoke joint 202at its midsection coupled to a yoke arm structure assembly 216, which inturn may comprise a left yoke arm 218 and a right yoke arm 220 as shown.In some embodiments, other yoke configurations, such as single arms orarms having different shapes and/or sizes may be used. The yoke armstructure assembly 216 may be used as a connecting member between theyoke 198 and a wheel arm structure assembly 222, which may be part of aground follower assembly. The ground follower assembly may furtherinclude wheel arm structure assembly 222, wrist assembly 206, and leftand right wheel arms 224 and 226. The lower end of the yoke armstructure assembly 216 may be coupled to the wheel arm structureassembly 222, using wrist joint assembly 206, which may comprise twomating halves, a left wheel arm 224, and a right wheel arm 226. Leftwheel 212 and right wheel 214 may serve as ground follower elements inthis embodiment. The yoke arm structure assembly 216 may be formed bythe two mating halves (the left yoke arm 218 and the right yoke arm 220)joined around a shaft-end formed in the wheel arm structure assembly222. Additional details of the wrist joint assembly embodiment 206 arefurther detailed in FIG. 15, FIG. 16, and FIG. 17. Left wheel 212 andright wheel 214 may serve as ground follower elements as shown.

In the embodiment of FIG. 12, the shapes and angles of the yoke armstructure assembly 216 and the wheel arm structure assembly 222 may varyin design. The central area of a wheel axle assembly 228 or the rear orlower area of the wheel arm structure assembly 222 may be augmented withone or more instances of a counterweight, such as brass counterweight230 to improve traction and self-righting movement when traversingterrain. In FIG. 12, the yoke arm structure assembly 216 and the wheelarm structure assembly 222 may be configured as shown to form an angleto provide better stability for the left wheel 212 and the right wheel214. As further shown in FIG. 12, each half of the wheel arm structureassembly 222 may be formed with an extended arm below the centerline ofthe wheel axle assembly 228; at the lower end of which arm acounterweight 230 of brass or similar material may be seated to furtherimprove self-righting stability over the ground by adding rear-endweight.

The swivel action of the wrist joint assembly 206 allows the dual-wheelground tracking device 196 to better maintain ground contact for eachwheel on an uneven surface, and may also be used to enable thedual-wheel ground tracking device 196 to provide additional informationabout the slope of ground (in a cross-axis direction) being traversed,as well as providing additional motion information such as describedpreviously. This motion may be sensed by a sensor associated with thewrist joint assembly which may be configured to sense side-to-side orother movements. Separate instances of magnets and magnetic sensors,and/or other sensing elements, may be used for the left wheel 212 andthe right wheel 214.

Turning to FIG. 13, the dual wheel ground tracking device embodiment 196is shown from below (e.g., as would be seen looking up from the ground).As shown in this view, rotations which may be sensed include rotation200 around the central axis of the lower antenna enclosure 126(corresponding to the movements shown in FIG. 1B); rotation 204 aroundthe yoke joint 202 (corresponding to the movements shown in FIG. 1C);rotation 208 around the axis of the wrist joint assembly 206; as well asindividual rotations 210 for each of the left wheel 212 and the rightwheel 214, around the axis of the wheel axle assembly 228. A centralaxle bushing 232 of Delrin or similar material may be disposed at thecenter of the wheel axle assembly 228 between the left wheel 212 and theright wheel 214. On either side of the axle bushing 232 a formed stowagegrip 234 may be seated. The stowage grips 234 provide a mechanism forlatching a wheel assembly 236 against a locator mast 120 or otherstructure of a measurement device, by a friction grip when thedual-wheel ground tracking device 196 is not in use, for ease of stowageand portability.

A gap may be included between the left wheel 212 and the right wheel 214to function as a slot into which the locator mast 120 fits (with theyoke arm structure assembly 216 rotating around the yoke joint 202) forstorage and carrying, creating a more compact stowed assembly.Additionally, a series of bumps 235 formed in, or adhesively attachedto, the inside of each radial spoke of the left wheel 212 and the rightwheel 214 near the mid-point of the spoke may be used to provide afriction grip on either side of the locator mast 120 when the dual-wheelground tracking device 196 is folded against the locator 104 in a stowedconfiguration. The bumps 235 may be located on the inner rim of the leftwheel 212 and the right wheel 214, on the spokes, or both. At the bottomof the yoke arm structure assembly 216, a ground sensing assembly, suchas white LED 148 and the optical sensor 150 may be mounted, such as onthe inset optical sensor PCB 152.

In some embodiments, an optical mouse sensor 237 may optionally bemounted in a location near the ground in ordinary operation, such as onthe lower surface of the yoke arm structure 216. The optical mousesensor 237 may include an integrated LED and a simple imaging or camerachip with associated processing circuitry. In operation, the opticalmouse sensor 237 may be configured to capture images betweenapproximately 1500 and 7080 times per second, with typical resolution ofapproximately 800 to 1600 counts per inch. One example of such a sensoris the Agilent ADNS 3080. The optical mouse sensor 237 may be equippedwith auxiliary optics and a side-lit narrow-beam LED in the IR range ofapproximately 700-1000 nanometers. Image data from the optical mousesensor 237 may be processed on an associated circuit board to providefine-movement information which may then be integrated into the positionand orientation calculus for the dual-wheel ground tracking device 196.

Turning to FIG. 14, example rotational movements of the dual-wheelground tracking device embodiment 196 are shown from the left side. Forexample, rotation 200 around the axis of the locator mast 120 and thelower antenna enclosure 126 may be implemented using yoke 198. Therotation 204 of the yoke arm structure assembly 216 around the axis ofthe yoke joint 202 may be implemented by the yoke joint 202. Therotation 208 around the approximately horizontal axis of the wrist jointassembly 206 may be enabled by the wrist joint assembly 206. Each wheelrotation 210 relative to the wheel assembly 236 may be enabled by thewheel axle assembly 228.

Turning to FIG. 15 and FIG. 16, details of an exemplary embodiment of atwo wheel assembly configuration 236 of a ground follower assembly isshown. Wheel assembly 236 may include the left wheel 212 and the rightwheel 214 which may each include a wheel hub section, such as section238, on which may be seated an axle bushing 232, tubular incross-section and which may be composed of Delrin or like material. Thewheel axle assembly 228 may be formed by the left wheel hub section 238on the left wheel 212 (obscured in this view) and the counterpart rightwheel hub section 238 on the right wheel 214 in combination with theaxle bushing 232.

The resultant wheel axle assembly 228 as shown supports two of the wheelbushings 240 and two of the stowage grips 234. The wheel bushing 240associated with the left wheel 212 may contain the magnetic shield 162for the left wheel 212. The wheel bushing 240 associated with the rightwheel 214 may contains the magnetic shield 162 for the right wheel 214.A permanent magnet 164 associated with the left wheel 212 may be seatedwithin the magnetic shield 162 located in the hub of the left wheel 212.A permanent magnet 164 associated with the right wheel 214 may be seatedwithin the magnetic shield 162 located in the hub of the right wheel214. One of the magnetic sensors 168 mounted on one of the sensor PCBs170 with the metallic foil backing 174 may be mounted in each of theleft wheel arm 224 and the right wheel arm 226. The use of dual wheels,with separate sensor mechanisms, may be used to provide a more accuratemeasure of pivoting or turning (relative to a single wheel embodiment),and/or of tracking motion and orientation over uneven terrain where thewheels may not be rotating in the same degree. Dual wheel configurationsmay also be used to provide improved resolution and accuracy,particularly over rough terrain for direct linear measurement, such aswhen used with a measuring device for applications other than locating.

A wrist joint assembly 206 may be supported when the mating left yokearm 218 and the right yoke arm 220 of the yoke arm structure assembly216 are seated around a shaft (consisting of two mating wrist shaftsections 242) formed by mating the left wheel arm 224 and the rightwheel arm 226. The wrist shaft sections 242 so mated may be formed witha series of grooves such as 244. In assembly, a series of solid ridgessuch as 246 formed in the inner face of the left yoke arm 218 and rightyoke arm 220 may be configured to lock into grooves such as grooves 244,thereby providing a secure entrainment between the yoke 198 and the yokearm structure assembly 216 and the wheel arm structure assembly 222 (seeFIG. 12) and the wheel assembly 236.

A wrist swivel element of the wrist joint assembly 206 may be used toallow dual wheel configurations to keep both wheels on the ground andprovide additional information about the slope of the ground in a crossaxis direction. The wrist swivel element of the wrist joint assembly 206(see FIG. 14) may be limited in its travel by the grooves 244 and theridges 246. A magnetic shield 162 containing a permanent magnet 164 forthe wrist joint assembly 206 may be seated in the end of the assembledshaft formed by the left and right wrist shaft sections 242. Themagnetic sensor 168 for wrist joint assembly 206 may be mounted onsensor PCB 170 with the metallic foil backing 174 and may be seatedinside the forward ends of the right yoke arm 220 and the left yoke arm218, aligned with the end of the assembled shaft (shown moved awaytherefrom for clarity in FIG. 15).

Referring to FIG. 16, the yoke joint 202 may incorporate two instancesof a yoke bushing 248. The right-hand yoke bushing 248 may contain amagnetic shield 162 and a permanent magnet 164 associated with the yokejoint 202. The corresponding magnetic sensor 168 (on the separate sensorPCB 170 with a metallic foil backing 174 may be mounted in the forwardend of the right yoke arm 220, aligned with the central axis of the yokejoint 202.

Further in FIG. 16, a magnetic shield 162 and a permanent magnet 164associated with the adaptor port 160 (FIG. 8) are shown moved outsidethe adaptor port 160 (FIG. 8) for illustrative purposes. Thecorresponding magnetic sensor 168 seated on the sensor PCB 170 with themetallic foil backing 174 may be seated in the receptacle 172 in thecenter of the lower arm of the yoke 198.

A white LED 148 and an optical sensor 150 may be mounted on theunderside of the inset optical sensor PCB 152 (see FIG. 13).

Turning to FIG. 17, a shaft formed by the wrist shaft sections 242 maycontain a magnetic shield 162 of the wrist joint, with a permanentmagnet 164 in its forward end. A corresponding magnetic sensor 168 onthe sensor PCB 170 with the metallic foil backing 174 may be seatedwithin the joined right yoke arm 220 and left yoke arm 218, aligned withthe central axis of the wrist shaft sections 242 when assembled, toprovide measurement of the angle of the wrist joint assembly 206. Amagnetic shield 162 and a permanent magnet 164 for the yoke joint 202may be seated in the right hand yoke bushing 248, while a correspondingmagnetic sensor 168 and a corresponding sensor PCB 170 with a metallicfoil backing 174 may be attached to the right yoke arm 220 to providemeasurement of the angle of the yoke joint 202.

An arm PCB, which may be similar to that shown in FIG. 6, may optionallybe mounted in the right wheel arm 226 or the right yoke arm 220 and usedto mount sensors such as the magnetic sensor 168 for the yoke joint 202,and the sensor (not shown in this view) associated with the right wheel214, as well as other optional sensors, such as those shown in FIG. 6.

In FIG. 18, a magnetic sensor 168 and a sensor PCB 170 associated withthe wrist joint, with a metallic foil backing 174, are shown. They maybe located in proximity to and centrally aligned with the wrist joint'smagnetic shield 162 and its retained permanent magnet 164. A wrist jointassembly 206 enclosed by the left yoke arm 218 and the right yoke arm220, and including the wrist shaft section 242, is illustrated. Anangled extension of the right wheel arm 226 may hold a brasscounterweight 230 in a formed receptacle.

As in the previously described embodiment as illustrated in FIG. 5 andFIG. 6, an arm PCB (not shown) may be seated within a formed wheel armstructure assembly 222, or yoke arm structure assembly 216 (see FIG.15), and may be electrically connected to sensor PCBs 170 for themagnetic sensors 168 associated with the left wheel 212 and the rightwheel 214, the yoke joint 202 and the wrist joint assembly 206. As shownin FIG. 6, such a PCB may support optional additional sensors such as athree-axis gyro sensor, a GPS module, a three-axis compass IC, and athree-axis accelerometer, and/or may include a microprocessor or otherprocessing element or circuit.

Such a suite of sensors may be used to provide finer resolution in datawhen the device traverses different surface features such as expansionjoints, curbs, transitions from concrete to gravel, or other surfacetransitions. This functionality may be used to support integration oflocate data with maps or images, or correlating images to groundfeatures. As in earlier embodiments, wired or slip-ring or wirelessconnection elements (not shown) may be used to communicate sensor datato the locator 104 or to other computing processors or devices.

Some embodiments, such as those illustrated in FIG. 1 and FIG. 11, mayuse a battery in associated locator 104 or other measurement device forpower. In an alternate embodiment, separate battery receptacles suitablefor holding, for example, a pair of 18650 Li-Ion batteries or otherbatteries may be formed into the arm structures near the wheels of thedevice, which may also improve traction by increasing the weight appliedto the wheels.

The locator 104 in FIG. 1 and in FIG. 11 may house a CPU or otherprocessing element or circuit for collecting, processing and/or storingdetector and locate information, and may be provided with a thumb drive,flash memory or other mechanism for storing information for later uploadto a remote system. In an alternate embodiment, a Bluetooth IC or otherwireless device may be added to the main PCB of the device to transmitdata to a remote computing station for integration with maps and images.Alternatively, some integration may be done within the locator itselfand incorporated into the locator's display device, such as by use of agraphic overlay to assist in the locate process. The locator 104 may beassociated by Bluetooth wireless connectivity or other wirelessmechanisms with a smart device, such as a phone capable of interchangingdata with cloud-based servers used for post processing and integratingorientation and position data. (An example of such a configuration isillustrated in FIG. 20 and in FIG. 21).

In use, the data derived from the angle of the yoke joint 202 as well asother positional sensors may be used to compute the height above groundof the lower antenna enclosure 126 of the locator 104 (or otherreference positions on different measuring devices) to enhance theaccuracy of depth calculations for locator-detected buried conductors.This is illustrated in the example movements shown in FIG. 1C, wherevarious elevations E1, E2, and E3 of the lower antenna enclosure areshown. Calculation of the height may be determined by measurement of theangle between the ground follower assembly and a locator referenceelement, such as angles Θ1, Θ2 or Θ3 along with the knowledge of theswing-arm length or fixed distance between the wheel 116 and locator104.

Captured X, Y and Z data provided by the various magnetic sensors 168also enable the system to correlate locate information againstphotographs, maps and as-builts and correct them. Such processing mayoccur in on-board microprocessors or at remote computing stations towhich data is transmitted through wireless devices, a wired networkconnection, or some removable device such as a thumb drive, for example.

Turning to FIG. 19, a block diagram 1900 illustrating an exampleinterconnection between an individual permanent magnet 164 and anexample of the magnetic sensor 168, in this instance the MelexisMLX90333 tri-axis sensor chip being used in serial output mode. TheMelexis MLX90333 uses four conventional Hall plates located under theperimeter of an integrated magneto-concentrator in a CMOS integratedcircuit to measure magnetic field components. The magneto-concentratoris deposited on the CMOS integrated circuit during fabrication.

The external magnetic field of the permanent magnet 164 causes amagnetic flux through the front end of magnetic sensor 168. Inparticular, the external Z component of the field causes radial fluxcomponent in the magneto-concentrator which is in turn sensed to a havea horizontal component in each of the four Hall plates. Externalmagnetic fields parallel to the plane of the magneto-concentrator andthe CMOS integrated circuit cause magnetic fluxes in the Hall platesthat have an opposite sign in at least one Hall plate when compared tothe fluxes produced by the vertical component. The outputs of the fourseparate Hall plates may be added and subtracted to provide threesignals proportional to the three components (Hx, Hy, and Hz) of theexternal magnetic field.

The output mode parameter “XYZ” may be programmable to enable outputdata frames containing X, Y and Z values when XYZ is set to 1, orcontaining Alpha and Beta angle values when XYZ is set to 0. Samplingrates depend on programmable slow/fast mode selection setting the unit'smaster clock to 7 or 20 MHz respectively with samples typicallyoccurring at 200 microseconds in fast mode and at 600 microseconds inslow mode.

Turning to FIG. 20, a block diagram of an embodiment 2000 of a processflow for integrating motion sensing signals is illustrated. Process flowdiagram 2000 illustrates example functions that may be used to integratedata from motion and/or rotation sensors, such as magnetic sensors 168as described previously herein. For example, magnetic sensors 168 may beconnected via an SPI bus or other interface circuit to a processorelement, such as microcontroller 182, of a ground tracking device, suchas dual-wheel ground tracking device 196, where the sensor signal may befurther processed and/or forwarded or relayed by wired or wirelessconnections to a measurement device, such as locator 104. In a typicalimplementation, the measurement device, such as locator 104, includes aseparate processing circuit (not shown), which may include amicrocontroller, microprocessor, ASIC, DSP, or other programmabledevice, along with memory and other associated circuit elements. Themeasurement device processing circuit may be configured to computelocation, motion, and/or orientation information and updates, and maystore this information in memory and/or may display a representation ofthe information on a display element, such as locator display 250. Thelocator 104 may optionally be linked to a smart device 252 such as asmart phone, PDA, tablet device, notebook computer, or other smartdevice incorporating a WAN modem 254, cellular link, or other wirelesscommunication links in which captured sensor data may be packetized andtransmitted to the cloud 256 of internetworked servers for furtherprocessing, storing, remote access and/or remote display, and/orrelaying. The locator or other measurement device may include a localstorage device interface, such as a USB or other port. For example, alocal storage device 258 connected to locator 104, such as a thumb driveor other storage device such as a USB-connected flash memory, forexample, may be used.

Referring to FIG. 21, the illustrated dual-wheel ground tracking deviceembodiment 196 may include a gyroscopic sensor, such as three-axisgyroscopic sensor IC 184, a compass element, such as three-axis compassIC 188, one or more accelerometers, such as three-axis accelerometer IC190, a satellite or terrestrial location device, such as a GPS module186, an optical sensor element, such as optical sensor 150, and/or anoptical mouse sensor, such as optical mouse sensor 237. An imaging orcamera element, such as a two- or three-dimensional camera 260 mayoptionally be mounted on the ground follower assembly, such as at aforward edge of a yoke element, such as the C-shaped yoke 112, toprovide additional imagery used in detecting ground features and/orsurfaces.

Input from sensors such as the magnetic sensors 168 may also beprocessed within a ground tracking device, such as embodiments 110and/or 196 as described previously herein, using an onboard groundtracking device processing element, such as microcontroller 182 or otherprocessor or programmable devices or signal processing circuits. Aground tracking device wireless connection element, such as an on-boardBluetooth relay 261, may be used to implement a data link to a separatereceiver element, such as Bluetooth link 262, which may be located onthe measurement device, such as locator 104 in the illustratedconfigurations.

The multi-dimensional antenna coils of locator 104 may be used to deriveEM sensor data 264. Other measurement devices may provide alternatesensor data or information. The sensor data may then be relayed from thelocator 104 or other measurement device using Bluetooth link 262 andBluetooth relay 261 to an optional associated smart device 252, such asa smart phone or similar device. The smart device 252 in this examplemay be equipped with a Bluetooth link 266, as well as typicallyincluding an inertial navigation subsystem 268 and a GPS module 270 ofits own. The smart device 252 may run a specific Ground Trackingsoftware application 272 designed to integrate multiple data streamsfrom the ground tracking device and its own sensors, and to transmitdata packets using a wireless data link, such as 3G data link 274. Datatransfer from the smart device 252 by the 3G data link 274 enables datato be sent to and received from one or more post-processing servers 276located in the internetworked cloud. Additional sensors may beoptionally included depending on application, including an acousticrange finder, a ground-penetrating radar used in conjunction with anoptical or laser range-finder, a barometric pressure sensor, a humiditysensor, and an RFID receiver. Sensor data from these additional sensorsmay be integrated with the various types of sensor data describedpreviously herein to generate additional position, motion, location,and/or related data or information.

Alternative configurations will be apparent to one skilled in the art,such as utilizing the smart device's GPS module 270 and omitting the GPSmodule 186 in the dual-wheel ground tracking device 196, or embeddingthe smart device's 252 components into the dual-wheel ground trackingdevice 196 or the locator 104, for example. Accordingly, theconfigurations of elements shown in the appended figures are providedfor purposes of explanation, not limitation.

Turning to FIG. 22 a flow chart illustrates an embodiment of a process2200 for sensor data integration. The process may include aninitialization process 278, a system interrupt process 280, aread-and-calculate process 282, and a Bluetooth data acquisition process284. In the initialization process 278 the system time and all systemsensors, optionally including an on-board camera for ground surfaceanalysis, may be initialized. The system interrupt process 280 may beginwith the interrupt being enabled and listening for an interrupt signal,while its value is “1.” When an interrupt signal is received, dependingon the particular sensors used, the magnetic sensor data for magneticsensors 1 to n may be read, the accelerometer values may be read, thevalues from the optical mouse sensor may be read, the gyroscopic valuesmay be read, and the results of the Bluetooth data acquisition process284, which acquires data provided from the locator, may be read. Thenumber n of magnetic sensors may vary with design.

One set of estimates of location and orientation may be derived from thedata recorded from the magnetic sensors 168, and a second set ofcalculations of location and orientation may be done based on dataderived from the navigational components (e.g., the three-axisaccelerometer 190, the three-axis gyroscopic sensor IC 184, thethree-axis compass IC 188, and the optical mouse sensor 229 as shown inFIG. 21). A filtering algorithm for a time series of imprecise datausing a statistical model in analyzing error, or Kalman filter, may beapplied to the two sets of computed locational data, and the estimate oflocation and orientation may be optimized. Optional image data, where anon-board camera or other imaging element is employed, may be processedthrough a processing function such as a scale-invariant featuretransform (SIFT) or a photo-stitching algorithm to enable pattern andfeature differentiation and/or image-stitching as needed. Such ananalysis may be used to support ground feature recognition and/orsurface differentiation in post-processing.

Assembled data packets may be transmitted using a Bluetooth relay 261 orother wireless communication link element of the ground tracking device,and the Bluetooth link 266 or other wireless link of the associatedsmart device 252 (as shown in FIG. 21). The interrupt may then be thenreset. The Bluetooth data acquisition process 284 may have receiveddetection data and any other sensor data from the Bluetooth link 266 ofthe locator 104. This may be done in parallel with the system interruptprocess described above. The detection data and other sensor data may bestored, and the data may be time-tagged in data packets locally withinthe ground tracking device so that they can be read during theread-and-calculate process 282. Other configurations of the system mayuse alternative methods of data transfer, such as a physicallytransferred removable memory device such as a USB thumb drive, which canthen be used to transfer data to a desktop or notebook computer, networkserver, tablet, or other device, for example.

Turning to FIG. 23, graphs 2300A and 2300B illustrating example datafrom a three-axis accelerometer IC 190 (as shown in FIG. 21) todifferentiate ground surface textures are illustrated. The accelerometeroutput data is shown in Graph 2300A for X axis acceleration in anexample transition from tile to doormat surfaces and in Graph 2300B forcorresponding Y axis acceleration. Graphs 2300A and 2300B representsignals associated with the movement of an example dual wheel groundtracking device, such as device 196 in system 194, while transitioningfrom a tile surface to a rough-textured doormat. The transition at the3.25-second mark in the signal voltage can be seen to mark a sharpincrease in signal and a change in pattern. In various embodiments, suchsignals can be determined for various ground or surface textures andstored for subsequent processing, such as for comparison to sensed dataas described previously herein to determine a particular type or classof surface. This processing may be done in a ground tracking device,locator or other measurement device, in post-processing, such as on acomputer or other processing system, or in various combinations of theseor other elements.

Turning to FIG. 24, Graphs 2400A, 2400B, 2400C, and 2400D illustratingsimilar data representing movement of an example ground tracking deviceover a grass terrain are shown. In this example, the data was generatedfrom a two wheel ground tracking device; however, similar data may begenerated from an embodiment using a single wheel ground followerelement or other configuration (such as a spherical embodiment). Theexample graphs are presented in two scales for the same data set. Thegraph 2400A illustrates X-axis samples from sample times tagged 1.65 to1.85 seconds. The graph 2400B illustrates corresponding Y-axis samples.Graphs 2400C and 2400D represent corresponding X and Y samples taggedfrom times 1.69 to 1.70 seconds (zoomed in from 2400A and 2400B with amoving average line added). The contrast in X and Y movement values canbe seen more clearly as the scale of the graph is reduced. Thesevariations in acceleration may be Kalman filtered to estimate motion orposition changes, such as elevation changes and map depressions, berms,and curb steps, and/or other features above buried utilities.

In some embodiments, one or more low powered transmitting dipole sondes,such as shown in embodiment 2500 of FIG. 25, may be incorporated in orattached to a ground follower element, such as the wheel 116 of FIG. 2,or alternately one or more transmitting dipole sondes, such as coils2510, may be attached to each of the left wheel 212 and the right wheel214 as shown in FIG. 25, which corresponds with the dual wheel groundtracking device embodiment of FIG. 11. These may include coils wound onspokes, such as dipole coils 2510 placed on left and right wheels asshown in FIG. 25, or placed on other elements of the wheels. Therotation and relative position of each of these transmitting dipolesondes may be sensed, such as by periodically or continuously beingtracked by in the locator 104 (for example, in a typical configurationwith a ground tracking device coupled to a locator, the locator deviceincludes the capability of measuring signals from sondes and can measuresignals from additional sondes disposed on the wheel(s), such as shownin FIG. 25).

The transmitting dipole sondes may be attached in various positions onthe wheels. In an exemplary embodiment, each sonde may be attached sothat it is centered on the axis of rotation of each wheel and so thatthe dipole axis of each attached sonde is orthogonal to the wheel axisof rotation in such a manner that the dipole axis is centered on androtates about the axis of rotation of the wheel it is attached to. Eachsonde may have a uniquely identifiable electromagnetic signal which maybe coded by coding mechanisms known or developed in the art. Forexample, each wheel sonde might simply transmit at a unique frequency.

Each wheel sonde may be battery powered, thereby avoiding the need forwired connections to locator 104. Each sonde may have a motion switch toautomatically enable transmission during use and stop transmission aftersome period of time of no rotation thereby conserving battery power. Thetransmitted signal from each sonde may additionally be modulated bymechanisms to encode information from other sensors such asaccelerometers, gyros, compasses, and the like. The dipole may beconstructed in two parts with a pair of identical coils wired in seriesmounted onto or embedded into any opposite pair of wheel spokes, therebyeffectively creating a single dipole field centered on the wheel axis ofrotation.

Various example embodiments have been described previously herein toprovide ground tracking devices that may be coupled to a locator orother measurement device. The ground tracking devices may be configuredwith a ground follower assembly, which may use an element such as one ormore wheels, a sphere, or other mechanisms to follow the ground or othersurfaces and provide sensed motion signals in multiple axes ordimensions. The motion signals may be processed in a processing circuitof the ground follower assembly to filter, correlate, generate motionand/or position data, and/or integrate the motion signals with othersensor data or information. The motion signals may be provided, eitheras raw signals or processed signals or data to the attached measurementdevice for further processing and/or data storage. Other combinations ofthe various aspects, elements, components, features, and/or functionsdescribed previously herein may be combined in various configurations.

In addition, details regarding additional aspects, elements, components,features, functions, apparatus, and/or methods which may be used inconjunction with the embodiments described previously herein in variousimplementations are described in the related applications of theassignee of the instant application.

In some configurations, the devices, elements, mechanisms, or apparatusmay include means for performing various functions as described herein,such as are illustrated in the appended drawing figures. Theaforementioned means may be, for example, mechanical elements such aswheels or other ground follower elements, sensor elements, processor orprocessors and associated memory in which embodiments reside, such as inprocessing elements, on circuit boards or substrates, or in otherelectronic configurations performing the functions recited by theaforementioned means. The aforementioned means may include anon-transitory storage medium including instructions for use by aprocessor to implement, in whole or in part, the various sensing andmeasurement functions described previously herein. In another aspect,the aforementioned means may be a module or apparatus configured toperform the functions recited by the aforementioned means.

In one or more exemplary embodiments, the various data collection,measurement, storage and signal processing functions, methods andprocesses described herein and/or in the related applications may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on or encoded asone or more instructions or code on a computer-readable medium.Computer-readable media includes computer storage media. Storage mediamay be any available media that can be accessed by a computer. By way ofexample, and not limitation, such computer-readable media can includeRAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic diskstorage or other magnetic storage devices, or any other medium that canbe used to carry or store desired program code in the form ofinstructions or data structures and that can be accessed by a computer.Disk and disc, as used herein, include compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

It is understood that the specific order or hierarchy of steps or stagesin the processes and methods disclosed are examples of exemplaryapproaches. Based upon design preferences, it is understood that thespecific order or hierarchy of steps in the processes may be rearrangedwhile remaining within the scope of the present disclosure. Anyaccompanying process or method claims present elements of the varioussteps in a sample order, however, this is not meant to be limitingunless specifically noted.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Toclearly illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. Skilled artisans may implement the describedfunctionality in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the disclosure. In some embodimentsmechanical elements and functions, such as ground follower assemblies,yoke assemblies, or other mechanical elements may be replaced, in wholeor in part, by other elements, such as acoustic or optical elements. Forexample, in some embodiments, some or all of the mechanical elements ofa ground follower assembly as described previously herein may includeacoustic and/or optical ground movement detection elements in place ofor in addition to mechanical elements such as wheels and yokes.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein may be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration. In some implementations, processors may be processorssuch as communication processors, specifically designed for implementingfunctionality in communication devices or other mobile or portabledevices.

The steps or stages of a method, process or algorithm described inconnection with the embodiments disclosed herein may be embodieddirectly in hardware, in a software module executed by a processor, orin a combination of the two. A software module may reside in RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, harddisk, a removable disk, a CD-ROM, or any other form of storage mediumknown in the art. An exemplary storage medium is coupled to theprocessor such that the processor can read information from, and writeinformation to, the storage medium. In the alternative, the storagemedium may be integral to the processor. The processor and the storagemedium may reside in an ASIC. The ASIC may reside in a user terminal. Inthe alternative, the processor and the storage medium may reside asdiscrete components in a user terminal.

The scope of the present invention is not intended to be limited to theaspects shown and described previously herein, but should be accordedthe full scope consistent with the language of the claims, whereinreference to an element in the singular is not intended to mean “one andonly one” unless specifically so stated, but rather “one or more”.Unless specifically stated otherwise, the term “some” refers to one ormore. A phrase referring to “at least one of” a list of items refers toany combination of those items, including single members. As an example,“at least one of: a, b, or c” is intended to cover: a; b; c; a and b; aand c; b and c; and a, b and c.

The previous description of the disclosed aspects is provided to enableany person skilled in the art to make or use the present invention.Various modifications to these aspects will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other aspects without departing from the spirit or scope ofthe disclosure. Thus, the disclosure is not intended to be limited tothe aspects shown herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein. Itis intended that the following claims and their equivalents define thescope of the invention.

We claim:
 1. A device for locating buried utilities, comprising: autility locator; and a ground follower assembly mechanically coupled tothe utility locator with a mounting assembly adapted to roll and pivotin conjunction with user-actuated movement of the utility locator over alocating surface, wherein the ground follower assembly generates one ormore dipole magnetic field output signals representative of a motion ofthe utility locator over a ground surface in two or more axes of motionand wherein the utility locator receives the one or more magnetic fieldsignals and determines position or motion information of the groundfollower based at least in part on the one or more received magneticfield signals.
 2. The device of claim 1, wherein the mounting assemblydetachedly mounts the ground follower assembly to the utility locator.3. The device of claim 1, wherein the ground follower assembly comprisesa yoke element and a swing-arm element, and the mounting assemblyincludes a bracket for detachably connecting the yoke element to theutility locator.
 4. The device of claim 1, wherein the position ormotion information is stored in a memory of the utility locator inassociation with buried object data determined in the locator.
 5. Thedevice of claim 1, wherein the utility locator receives the one or moremagnetic field signals at a plurality of three-axis magnetic fieldsensors disposed in the locator.
 6. The device of claim 1, wherein theground follower assembly is mechanically coupled to the utility locatorusing a yoke assembly.
 7. The device of claim 6, wherein the groundfollower assembly comprises one or more wheels positioned on the groundsurface during operation to follow the ground surface.
 8. The device ofclaim 7, further comprising a surface sensing apparatus to provide anoutput signal usable to determine a ground surface characteristic. 9.The device of claim 8, wherein the surface sensing apparatus comprises alight sensor.
 10. The device of claim 9, wherein the light sensor is animager for generating still or video images.
 11. The device of claim 10,further comprising a lighting element to illuminate the ground surfacein proximity to an area being imaged by the imager.
 12. The device ofclaim 11, wherein the lighting element comprises an LED array.
 13. Thedevice of claim 12, further comprising an accelerometer to provide anacceleration output signal to a processing element of the locator,wherein the position or motion information is further based on theacceleration output signal.
 14. The device of claim 12, furthercomprising a compass sensor to provide a compass output signal to aprocessing element of the locator, wherein the position or motioninformation is further based on the compass output signal.
 15. Thedevice of claim 12, further comprising a GPS receiver to provide apositional output signal to a processing element of the locator, whereinthe position or motion information is further based on the GPSpositional output signal.